CARACAS, Venezuela — Gunmen opened fire on students returning from a march Wednesday in which 80,000 people denounced President Hugo Chavez’s attempts to expand his power. At least eight people were injured, including one by gunfire, officials said.

Photographers for The Associated Press saw at least two gunmen — one wearing a ski mask and another covering his face with a T-shirt — firing handguns at the anti-Chavez crowd. Terrified students ran through the campus as ambulances arrived.

National Guard troops gathered outside the Central University of Venezuela, the nation’s largest and a center for opposition to Chavez’s government. Venezuelan law bars state security forces from entering the campus, but Luis Acuna, the minister of higher education, said they could be called in if the university requests them.

Antonio Rivero, director of Venezuela’s Civil Defense agency, told local Union Radio that at least eight people were injured, including one by gunfire, and that no one had been killed. Earlier, Rivero said he had been informed that one person had died in the violence.

The violence broke out after anti-Chavez demonstrators — led by university students — marched peacefully to the Supreme Court to protest constitutional changes that Venezuelans will consider in a December referendum.

Proposals increase presidential powerThe amendments would abolish presidential term limits, give the president control over the Central Bank and let him create new provinces governed by handpicked officials.

The protesters demand the referendum be suspended, saying the amendments would weaken civil liberties in one of South America’s oldest democracies and give Chavez unprecedented power to declare states of emergency.

Chavez, who was first elected in 1998, denies the reforms threaten freedom. He says they would instead move Venezuela toward what he calls “21st century socialism.”

The Supreme Court is unlikely to act on the students’ demands, given that pro-Chavez lawmakers appointed all 32 of its justices.

Hundreds of National Guardsmen and police in riot gear were posted along the march route to prevent clashes between protesters and Chavez sympathizers, but they were restricted from entering the campus.